The bitter power of regret fuels the heartfelt comedy dramatics of Safety Not Guaranteed.

Films have been based on many different sources, but it’s hard to think of a film based on a classified advertisement. Safety Not Guaranteed does just that. The ad in question first appeared in Backwoods Home Magazine in 1997, where a supposed time traveller is looking for a partner to go back in time with him. Oh, and they must bring their own weapon.

Of course it’s fictitious (the man behind the ad said it was written as a joke to fill in ad space), but that didn’t stop the ad from becoming an online phenomenon and now the inspiration for a heartfelt and entertaining film.

Safety Not Guaranteed is directed Colin Trevorrow and written Derek Connolly, a tandem whose most known credit to this point is the TV movie Gary: Under Crisis. Safety Not Guaranteed is sure to change all of that.

The film focuses on Darius (Aubrey Plaza) a magazine intern not happy with her station in life and still grieving the death of her mother years earlier. When senior journalist Jeff (Jake M. Johnson) takes on an assignment to track down the man behind that time travel ad, Darius eagerly volunteers to help. Their investigation leads them to Kenneth (Mark Duplass), an isolated and eccentric sad-sap who finds an unlikely connection with Darius.

While the films unique concept will be its draw, there is no doubt that many will praise its central relationship as its strength. The offbeat personalities of Plaza and Duplass mesh very well and anchor a movie that could have easily been whisked away by its eccentricities.

Plaza (who has been on the cusp of stardom for a while now) has found a leading role that suits her deadpan, sarcastic vibe (imagine Janeane Garofalo but without the bitter baggage), yet also brings out a vulnerability that she wears well.

Fragility is something that Duplass also successfully depicts, yet in this case it’s veiled in a macho character in Kenneth who has seen way to many sci-fi action movies and has too much time on his hands, his paranoia blending with a hopeless rationalism about the power to change the past.

Yet despite his clearly delusional frame, Kenneth’s search for redemption taps into a strong emotion in all of us: regret. That fantasy of going back in time to right the wrongs in our lives makes Darius - and we the audience - pray that Kenneth does find a way to mend his old wounds, whether through a time portal or good old fashioned purging.

Part of what makes Safety Not Guaranteed such a great watch is how Trevorrow and Connolly tease the possibility that Kenneth may not be the crackpot we think he is. Hope is a powerful thing and Safety Not Guaranteed delivers in its tale of longing, deliverance and connection during the here and now.